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Body mass index and breast cancer: analysis of a nation-wide population-based prospective cohort study on 1 393 985 Taiwanese women.

ABSTRACT: Asian women have a younger age at onset of breast cancer and a lower body mass index (BMI) than Western women. The link between obesity and risk of breast cancer in Asian women is still elusive. We aimed to investigate the effect of BMI on the risk of incident breast cancer in Taiwanese women.A total of 1,393,985 women who had been cancer-free before recruitment and attended a nation-wide Taiwanese breast cancer-screening program between 1999 and 2009 were enrolled using a prospective cohort study. Obesity and other relevant variables (such as menopause status and other biochemical markers) were collected through in-person interviews, anthropometric measurements and blood samples at first screen. Incident breast cancers during follow-up were ascertained through the linkage of the cohort with the National Cancer Registry and the National Death Certification System.A total of 6969 and 7039 incident breast cancer cases were identified among women enrolled before and after menopause, respectively. Compared with a BMI range of 18.5-23.9 kg m(-)(2), the incremental level of BMI in the enrolled women before menopause revealed a lack of statistically significant association with the risk of incident breast cancer (adjusted hazard ratio=0.94, 0.98, 1.02, 1.01 and 0.82 for BMI <18.5, 24-26.9, 27-29.9, 30-34.9 and ⩾35, respectively), but the incremental level of BMI in the enrolled women after menopause led to a statistically significant incremental increase in the risk of breast cancer (adjusted hazard ratio=0.78, 1.19, 1.31, 1.53 and 1.65 for BMI <18.5, 24-26.9, 27-29.9, 30-34.9 and ⩾35, respectively) after adjusting for other explanatory risk factors.Obesity acts mainly as an influential promoter of the development of late-onset breast cancer after menopause in Taiwanese women.

SUBMITTER: Chen MJ

PROVIDER: S-EPMC4786735 | biostudies-other | 2016 Mar

REPOSITORIES: biostudies-other

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Project description:BackgroundAdiposity is associated with many adverse health outcomes but little direct evidence exists about its impact on the use of health care services. We aim to describe the relationship between body mass index (BMI) and rates of hospital admission in middle-aged UK women.MethodsAmong 1,251,619 Million Women Study participants, 50- to 64-years old at entry into the study, routine data on hospital admissions were used to estimate hospitalization rates according to BMI after standardization for age, region of recruitment, socioeconomic status, reproductive history, smoking status, hormonal therapy use and alcohol intake. Proportional hazards models were used to estimate adjusted relative risks of hospitalization separately for 25 common types of admission.ResultsDuring an average of 9.2 years follow-up, there were 2,834,016 incident hospital admissions. In women with BMIs (in kg/m2) of <22.5, 22.5 to <25, 25 to <30, 30 to <35 and 35+ standardized admission rates (and 95% confidence intervals (CIs)) per woman over a 10-year period were 2.4 (2.4 to 2.4), 2.4 (2.3 to 2.4), 2.6 (2.6 to 2.6), 3.0 (3.0 to 3.0) and 3.5 (3.4 to 3.5), respectively (P-value for heterogeneity <0.001). The relative increase in admission rates per 5 kg/m2 increase in BMI was 1.12 (1.12 to 1.13). This relationship did not vary materially by age. Corresponding average durations of stay (in days) per hospital visit within the same categories of BMI were: 3.1 (3.1 to 3.2), 2.8 (2.7 to 2.8), 2.9 (2.9 to 2.9), 3.2 (3.1 to 3.2) and 3.8 (3.7 to 3.8), respectively (P <0.001).Significant increases in the risk of admission with increasing BMI were observed for 19 of the 25 types of hospital admission considered. BMI was most strongly associated with admissions with diabetes, knee-replacement, gallbladder disease and venous thromboembolism, but marked associations were found with many other common categories of admission including cataracts, carpal tunnel syndrome and diverticulitis.ConclusionsAmong women 50- to 84-years old in England, around one in eight hospital admissions are likely to be attributable to overweight or obesity, translating to around 420,000 extra hospital admissions and two million extra days spent in hospital, annually.

Project description:BackgroundA high body mass index (BMI) is associated with an increased risk of mortality from coronary heart disease (CHD); however, a low BMI may also be associated with an increased mortality risk. There is limited information on the relation of incident CHD risk across a wide range of BMI, particularly in women. We examined the relation between BMI and incident CHD overall and across different risk factors of the disease in the Million Women Study.Methods1.2 million women (mean age=56 years) participants without heart disease, stroke, or cancer (except non-melanoma skin cancer) at baseline (1996 to 2001) were followed prospectively for 9 years on average. Adjusted relative risks and 20-year cumulative incidence from age 55 to 74 years were calculated for CHD using Cox regression.ResultsAfter excluding the first 4 years of follow-up, we found that 32,465 women had a first coronary event (hospitalization or death) during follow-up. The adjusted relative risk for incident CHD per 5 kg/m2 increase in BMI was 1.23 (95% confidence interval (CI) 1.22 to 1.25). The cumulative incidence of CHD from age 55 to 74 years increased progressively with BMI, from 1 in 11 (95% CI 1 in 10 to 12) for BMI of 20 kg/m2, to 1 in 6(95% CI 1 in 5 to 7) for BMI of 34 kg/m2. A 10 kg/m2 increase in BMI conferred a similar risk to a 5-year increment in chronological age. The 20 year cumulative incidence increased with BMI in smokers and non-smokers, alcohol drinkers and non-drinkers, physically active and inactive, and in the upper and lower socioeconomic classes. In contrast to incident disease, the relation between BMI and CHD mortality (n=2,431) was J-shaped. For the less than 20 kg/m2 and ≥35 kg/m2 BMI categories, the respective relative risks were 1.27 (95% CI 1.06 to 1.53) and 2.84 (95% CI 2.51 to 3.21) for CHD deaths, and 0.89 (95% CI 0.83 to 0.94) and 1.85 (95% CI 1.78 to 1.92) for incident CHD.ConclusionsCHD incidence in women increases progressively with BMI, an association consistently seen in different subgroups. The shape of the relation with BMI differs for incident and fatal disease.

Project description:BackgroundExcess weight is associated with poor health and increased health-care costs. However, a detailed understanding of the effects of excess weight on total hospital costs and costs for different health conditions is needed.MethodsWomen in England aged 50-64 years were recruited into the prospective Million Women Study cohort in 1996-2001 through 60 NHS breast cancer screening centres. Participants were followed up and annual hospital costs and admission rates were estimated for April 1, 2006, to March 31, 2011, in relation to body-mass index (BMI) at recruitment, overall and for categories of health conditions defined by the International Classification of Diseases 10th revision chapter of the primary diagnosis at admission. Associations of BMI with hospital costs were projected to the 2013 population of women aged 55-79 years in England.Findings1 093 866 women who provided information on height and weight, had a BMI of at least 18·5 kg/m2, and had no previous cancer at recruitment, were followed up for an average of 4·9 years from April 1, 2006 (12·3 years from recruitment), during which time 1·84 million hospital admissions were recorded. Annual hospital costs were lowest for women with a BMI of 20·0 kg/m2 to less than 22·5 kg/m2 (£567 per woman per year, 99% CI 556-577). Every 2 kg/m2 increase in BMI above 20 kg/m2 was associated with a 7·4% (7·1-7·6) increase in annual hospital costs. Excess weight was associated with increased costs for all diagnostic categories, except respiratory conditions and fractures. £662 million (14·6%) of the estimated £4·5 billion of total annual hospital costs among all women aged 55-79 years in England was attributed to excess weight (BMI ≥25 kg/m2), of which £517 million (78%) arose from hospital admissions with procedures. £258 million (39%) of the costs attributed to excess weight were due to musculoskeletal admissions, mainly for knee replacement surgeries.InterpretationExcess body weight is associated with increased hospital costs for middle-aged and older women in England across a broad range of conditions, especially knee replacement surgery and diabetes. These results provide reliable up-to-date estimates of the health-care costs of excess weight and emphasise the need for investment to tackle this public health issue.FundingCancer Research UK; Medical Research Council; National Institute for Health Research.

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Body mass index and breast cancer: analysis of a nation-wide population-based prospective cohort study on 1 393 985 Taiwanese women.

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